Dunskey Castle in the far southwest corner of Scotland near Portpatrick. It's a great ruin in a stunning location.
This was another tour group that passed us while travelling from Chile to Bolivia to reach the Salar de Uyuni. The scenery was great the entire way.
Innischonnel Castle on an island in Loch Awe in the west of Scotland. Also known as Ardchonnel, it's an amazing ruin. I've been here twice to photograph it but I've never actually organized a trip to get inside. Maybe one day...